NOTE: Yeah, I'm no Xypherous, I'm not the most original person alive. I just made a tank with a kit that I would love to see in League. This is merely a super super rough draft of what I'm thinking of. I am still fiddling with a lore for him. Right now, he's a sort of animated golem that was originally made in the image of a god, the god of earth's wrath. Deino belonged to the civilization who worshipped this god and he was made in the hopes that the god might grant them its powers. However, the civilization was brutally attacked by its foes and collapsed. The entire city was leveled and left in ruins, save for Deino. Suddenly, Deino "awakens". For some reason, he has sentience, but he doesn't understand why. And for another strange reason, he can remember things, despite never having been alive before now. He can recall the screams of the dying, the clashing of weapons and the chanting of the victors. Deino grows to hate how humans behave, using his civilization and the war as examples of what is wrong with them. They created a strone object in the hopes that a god might grant them some kind of power, an idea that Deino finds ridiculous. How is a god going to give strength to weak and feeble creatures like humans simply because they made a statue? Deino's new mind tortures him. He can analyze the stupidity of humans, Unfortunately, his mind still fragile, he begins to propose a solution: absolute extinction of humans. He reasons that humans wage war on each other because they know their time is up, they seek self-destruction, yet they fail in eliminating themselves. He believes his existence is not without purpose: he is the humans' savior, come to relieve them from the pain of life. Hence, he begins his quest of going from city to city, destroying their foundations and slaughtering all those he finds. Each society that is found by him is left in ruins, with every stone ground to dust, earning him the nickname "The Rock Wrecker". So far, I'm just okay with this backstory, I might edit it or outright replace it with something else.
I took heavy inspiration from Pokemon actually. One day I suddenly thought of Rhydon and Rhyperior and said to myself "it would be so amazing if a rock-like rhino beast existed in League with a drilling horn mounted on his forehead" and that's how Deino was formed in my mind. And Pokemon fans will recognize the names "Stone's Edge" and "Rock Wrecker".